This invention relates to an adaptor for setting a disc which is of a smaller diameter than a standard type disc, such as an 8-cm Compact Disc, in a disc playback device such as a standard type Compact Disc player and, more particularly, to an adaptor of such type capable of attaching the detaching a disc easily and also capable of preventing disengagement of the adaptor from a disc.
A Compact Disc in the Compact Disc Digital Audio System (hereinafter abbreviated as "CD") has an outer diameter of 12 cm. There is however a CD of a smaller diameter of 8 cm which is called an 8-cm CD. If this 8-cm CD is played back by a standard CD player, there arise inconveniences such as that a disc is damaged during loading or unloading and that it sometimes does not come out of the CD player. For overcoming such inconveniences, there have been proposed various adaptors which are attached to an 8-cm CD so as to substantially enlarge its outer diameter to 12 cm and thereby enable the 8-cm CD to be handled in the same manner as the standard type CD.
FIG. 2 shows an example of such prior art adaptors. This adaptor 10 is constructed of an annular plate with a diameter of 12 cm, is formed with slits 15 in its inner peripheral portion, and also is formed with three tabs 11, 12 and 13. An 8-cm CD 14 is attached to the adaptor 10 by means of these tabs 11, 12 and 13. In attaching the 8-cm CD 14, the outer peripheral portion of the 8-cm CD 14 is held by the tab 11 and then by the tab 12 and then the third tab 13 is pulled outwardly by utilizing elasticity imparted to the adaptor 10 by the provision of the slits 15 to cause the 8-cm CD to be engaged by the third tab 13.
However, the prior art adaptor 10 has the following disadvantages:
i) Attaching and detaching of the 8-cm CD 14 are rather difficult and scratches and spots tend to occur on the 8-cm CD 14 during attaching and detaching. PA1 ii) Since this adaptor 10 is rotated with the 8-cm CD 14 during playback of the 8-cm CD 14, the adaptor 10 tends to be disengaged from the 8-cm CD 14 with resulting damage to the 8-cm CD 14 or to the CD player. PA1 iii) Since the prior art adaptor 10 is of such construction that the tabs 11, 12 and 13 respectively hold the 8-cm CD 14 vertically between their upper and lower projections, the portions of the 8-cm CD held by the tabs 11, 12 and 13 become three-layered structure and the thickness of these portions increases with a result that a standard thickness of 1.5 mm of a CD can no longer be maintained. PA1 iv) The adaptor 10 must be attached and detached each time the 8-cm CD is changed. PA1 v) Since the adaptor 10 is fixed to the 8-cm CD 14, a warp or deformation of the adaptor 10 produces a corresponding warp or deformation to the 8-cm CD 14 with resulting deterioration in the accuracy of reproduction.
It is, therefore, an object of the invention to provide an adaptor which facilitates attaching and detaching a disc and preventing disengagement of the adaptor from the disc during playback of the disc.